1. Field of the Invention
The invention relates to an axial flow fan.
2. Description of the Background Art
Axial flow fans are used as blowers in motor vehicles, wherein the axial flow fan is arranged in the direction of air flow downstream of a heat exchanger or a group of heat exchangers and suctions ambient air through the heat exchanger or heat exchangers for cooling purposes. The axial flow fan runs in a shroud ring, i.e., a stationary case, wherein the shroud ring is part of a shroud or a fan cowl, which adjoins the heat exchanger or the group of heat exchangers. The internal combustion engine of the motor vehicle as well as additional units of the internal combustion engine are arranged downstream of the axial flow fan in the direction of air flow, i.e., in its outflow field, which form non-uniform obstacles in the outflow field of the axial flow fan. Due to the customary compact construction in the engine compartment of the motor vehicle, these obstacles, in particular the internal combustion engine are arranged at a small axial distance behind the axial flow fan, whereby effects of a blocking can result, in particular a pressure loss through a greater throttling, but also a pressure increase through diffuser effect. Furthermore, the air flow exiting the axial flow fan is affected by a swirl, which cannot be used for an additional pressure buildup—in fact the energy associated therewith is dissipated. Finally, the problem of recirculation also frequently occurs, i.e., the induction again of heated air that has exited from the axial flow fan. This leads to a deterioration of the cooling capacity.
Due to these problems, it has already been proposed that the outflow field of the axial flow fan should be influenced in a targeted manner, i.e., by a so-called outlet guide device or outlet guide elements.
In EP 1 443 216 A2, which corresponds to U.S. Pat. No. 6,827,547 B2, a cooling system for an internal combustion engine of a motor vehicle is disclosed, wherein a diffuser as well as exit-side flow guidance elements are arranged downstream of an axial flow fan circulating in a shroud ring. The shroud ring, which adjoins a fan cowl or shroud, encases the fan blades of the axial flow fan over their entire depth (axial extension), and the flow guidance elements running essentially in the radial direction are arranged downstream of the outflow edges of the fan blades in the direction of air flow, i.e., upstream of the fan exit plane. Thus a relatively large axial construction depth proves to be a disadvantage, since the depth of the fan blades and the depth of the flow guidance elements add up in the axial direction.
Through the applicant's DE 10 2006 037 628 A1, which is herein incorporated by reference, an outlet guide device for an axial flow fan arranged in a stationary manner is disclosed, which is arranged between a heat exchanger embodied as a coolant radiator and an internal combustion engine. The outlet guide device comprises on the one hand a diffuser and on the other hand flow guidance elements running essentially radially, which extend from the root of the fan blades to the outer diameter of the diffuser. The radial flow guidance elements and the diffuser are arranged downstream of the fan exit plane, so that that a relatively large axial construction depth results here too. This also applies to a further exemplary embodiment, in which flow guidance elements running radially are arranged radially outside the fan and the shroud ring.